Former Editor Andy Coulson Testifies in Hacking Trial

Reporters Kept Their Sources' Identities a Secret, He Said

LONDON—The former spokesman for British Prime Minister David Cameron on Monday took the stand for the first time in the monthslong phone-hacking trial, seeking to defend himself against accusations that he knew about the use of illegal tactics to pursue scoops while he was editor of a British tabloid.

Andy Coulson and six other defendants have pleaded not guilty to a number of charges related to a broad investigation into alleged illegal interception of phone messages. Mr. Coulson edited News Corp's now-defunct News of...